1. Field of the Invention
This invention relates to a method of and a device for raising flattened parallelepipedic blanks to form rectangular parallelepipeds with a square-shaped cross section in the course of their conveyance.
2. Description of Background Art
Conventionally, various paper containers are made to fit various purposes, e.g., disposable packing containers for containing liquid foods such as milk. The packing containers are supplied in the form of rimpled and flattened parallelepipedic packing container blanks. The bottoms of the containers are closed by an automatic packing machine. Thereafter, the blanks are formed into containers with an open top. Subsequently, liquid food, such as milk, may be charged at the charging station of the automatic packing machine.
In the case of packing container blanks, packing material is cut to have an outline that enables it to be reformed into a complete packing container without additional cutting. Rimples are formed in the blanks and the longitudinal sides are sealed to form a packing container blank with a square-shaped cross section. In effect, the blank is formed to be a flattened parallelepiped for the convenience of storage and transportation. The parallelepipedic blanks require a device for raising the flattened packing container blanks into blanks with a square-shaped cross section before charging the contents at the filling station of the automatic packing machine, in order to form blanks with a sealed bottom and an open top.
Several devices have been conceived to raise flattened packing container blanks into blanks with a square-shaped cross section. These devices are located at the mandrel wheel mount of the automatic packing machine (hereinafter called "packer"), and generally each packing container blank is taken out of an outlet end of a magazine that houses a pile of packing container blanks while being held by a suction head. During this time, packing container blanks are reformed to have a square-shaped cross section and transferred to the lifting conveyor to be loaded onto the mandrel of the rotating mandrel wheel one after another. At this station, the bottoms of the blanks are formed.
Such a device for forming blanks to have a square-shaped cross section with the help of cams and rollers during a rotational transfer of blanks which are held by the rotational transferring device of a suction head using a link mechanism is cited in the Japanese Patent Disclosure Report No. 57-163615. This device maintains the shape of the square-shaped cross section after changing its shape to a rhomb so that the rectangular parallelepipedic blank will not return to the flattened shape due to bending. Also, a device not using a suction head is reported in the Japanese Patent Disclosure Report No. 59-209512, wherein the device raises a packing container blank that is being transferred by conveyor to form a square-shaped cross section using arms and hooks. In such embodiment, overfolding of the section to a rhomb is prevented when forming the section to a square.